Put the code handling \} into a new function roff_cond_checkend()
and call that function not only from both places where copies
existed - when processing text lines and when processing request/macro
lines in conditional block scope - but also when closing a macro
definition request, such that this construction works:

.if n \{.de macroname
macro content
.. \} ignored arguments
.macroname

This fixes a bug reported by John Gardner <gardnerjohng at gmail dot com>.

While here, avoid a confusing decrement of the line scope counter
in roffnode_cleanscope() for conditional blocks that do not have
line scope in the first place (no functional change for this part).
Also improve validation of an internal invariant in roff_cblock()
and polish some comments.

When a conditional block is closed by putting "\}" on a text line
by itself (which is somewhat unusual but not invalid; most authors
use the empty macro line ".\}" instead), agree more closely with
groff and do not produce a double space in the output.

Quirk reported by millert@.

While here, tweak the rest of the function body of roff_cond_text()
to more closely match roff_cond_sub(). The subtly different handling
could make people (including myself) wonder whether there is any
point in being different. Testing shows there is not.

Messages of the -Wbase level now print STYLE:. Since this
causes horrible churn anyway, profit of the opportunity to stop
excessive testing, such that this is hopefully the last instance
of such churn. Consistently use OpenBSD RCS tags, blank .Os,
blank fourth .TH argument, and Mdocdate like everywhere else.
Use -Ios=OpenBSD for platform-independent predictable output.

cope with changes in BASE messages

churn related to the new style message about RCS ids

Move .sp to the roff modules. Enough infrastructure is in place
now that this actually saves code: -70 LOC.

Parser reorg:
Generate the first node on the roff level: .br
Fix some column numbers in diagnostic messages while here.

Clean up ERROR messages related to document structure and macros:
Hierarchical naming and mention macro names in messages.

When a conditional block is closed by putting "\}" on a text line
by itself (which is somewhat unusual but not invalid; most authors
use the empty macro line ".\}" instead), agree more closely with
groff and do not produce a double space in the output.

Quirk reported by millert@.

While here, tweak the rest of the function body of roff_cond_text()
to more closely match roff_cond_sub(). The subtly different handling
could make people (including myself) wonder whether there is any
point in being different. Testing shows there is not.

Messages of the -Wbase level now print STYLE:. Since this
causes horrible churn anyway, profit of the opportunity to stop
excessive testing, such that this is hopefully the last instance
of such churn. Consistently use OpenBSD RCS tags, blank .Os,
blank fourth .TH argument, and Mdocdate like everywhere else.
Use -Ios=OpenBSD for platform-independent predictable output.

cope with changes in BASE messages

churn related to the new style message about RCS ids

Move .sp to the roff modules. Enough infrastructure is in place
now that this actually saves code: -70 LOC.

Parser reorg:
Generate the first node on the roff level: .br
Fix some column numbers in diagnostic messages while here.

Clean up ERROR messages related to document structure and macros:
Hierarchical naming and mention macro names in messages.